The research was conducted by astrophysicists from Osaka University in Japan.

    Using the technique called "gravitational(重力的) microlensing", scientists turned their telescopes towards the centre of the Milky Way and detected this "lonely planet" moving in a extremely large orbit, which suggested it does not connect to any solar system.

    Then they estimated the total number of such wondering planets could be as many as 400 billion, based on the detection efficiency. This number far outnumbers the main-sequence stars such as our Sun.

    "This is an amazing result, and if it is right, the implications for planet formation are profound," says astronomer Debra Fischer at Yale University in New Haven, Connecticut.

    And scientist began to consider the possibility that liquid water could exist on this kind of unbound planets. "That might be an attractive possibility for life," said David Stevenson, a planetary scientist at the California Institute of Technology.(本文由在线英语听力室整理编辑)